HDD Western Digital™ Purple of 4 TBytes. Size: 3.5" (Width: 102 mm x Height: 26 mm x Depth / length: 147 mm). 64 MB cache. 5,400 rpm. Reading: 110 MB / s. SATA / 600 interface. Power: 15-pin connector. 24/7 continuous operation (MTBF: 1,000,000 hours).